Sunday, August 30, 2009

What's the difference - NXT-G 2.0 Image Formats

The LEGO MINDSTORMS NXT-G 2.0 software allows users to easily open, edit, and save images in a variety of formats, but what is the difference between formats? Why does it matter if I save an image as a .jpg file instead of a .ric file? Prepare to be enlightened...

(If you are just interested in the straight forward facts, skip down to the conclusion of this post)

First of all, no matter which format you save images as through NXT-G 2.0, the result will almost be the same! Only differences in the size of the file may effect a common computer user - have a look at the table below...

(On this table "Empty Image" means I didn't add anything to the image before saving, and "Full Image means I completely blackened my image before saving - all images saved using the Image Editor in NXT-G 2.0)

As you can see, .bmp images are the largest files at 19.8 Kilobytes (kb), and .jpg files are the smallest size at only 742 bytes! However, every image file except .jpg files have a constant size, for as you can see from my table, only the .jpg file changes in size between a full and empty image. Interestingly enough, .jpg files change in size depending on where the blackened areas are in the image, causing the .jpg file size to alter from around 741 bytes to around 2.5 Kilobytes. But considering how much disk space our computers have, who needs to worry!

Note: These image sizes are for images on a Windows XP
. The size of an image on the NXT is 0.9
Kilobytes (around 900 bytes).

The NXT only displays .ric files, and any imported image will need to be saved as a .ric file before you can use it on the NXT. Once saved as a .ric file, you can use your image through a Display Block:

Note: All images saved through NXT-G 2.0 will be saved to the folder:

C:\Program Files\LEGO

where the red writing represemts where you installed NXT-G 2.0 to if you changed any settings during installation.

All images created in the NXT-G 2.0 Image Editor have 100 x 64 pixel dimensions (width by height)

What should I use on my computer?

The .ric files are only useful for users downloading them to their NXT brick. What happens if you want to see what image you are downloading beforehand? You internet browser does not support viewing .ric files, so that leaves .jpg, .png, and .bmp files - which is best? The image file size table shown at the beginning of this post outlined the... file sizes, but what about other differences? Here are some other facts about using images on your computer:

* Use on: Photographs, Realistic Drawings
* Bad results on: Line and Letter Drawings
* Loses detail after every edit - becomes more blurred (check it out using MS paint or similar - on large images, as the .ric files do not show this effect))

* Use on: Line and Letter Drawings, Clipart, Computer Image Scans (E.g. When using an external scanner to load a piece of paper onto your computer)
* Bad results on: Photographs, Full colour images
* Doesn't lose detail after every edit

All of the above files formats are easily distibuted on the internet as well, as every internet browser can view them.

* Larger Files

* NXT-only file, distribute only to other NXT-G 2.0 users, or users with other software supporting .ric files (more to come on this)
* Web browsers will not view them - require download and import into NXT-G 2.0 or other supportive software

More info can be found on the web, a good, simple, but helpful website can be found here:

So, in conclusion:

* The NXT can only display .ric images
* No image viewers support .ric files - including internet browsers
* Once an image is saved as a .ric file through the NXT-G 2.0 Image Editor, it can be displayed on the NXT using a Display Block
* Images saved using the NXT-G 2.0 Image Editor can be located on your computer under the LEGO MINDSTORMS NXT\engine\Pictures directory where you installed NXT-G 2.0
* Images created in the NXT-G 2.0 Image Editor have 100 x 64 pixel dimensions
* On the XXT brick, .ric files are about 900 bytes in size

* On your computer, .JPG files have the smallest image size, and .bmp has the largest file size
* Saving an image used on the NXT as any other image file type will not change the content of the picture
* For big images on your computer, .jpg files should be photographs, and png pictures should be text and line drawings
* .JPG files with large dimensions will lose detail and become blurred after every saved edit

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